it sounds like you have a Win 10 PC with a thunderbolt 3 port, and you are using the OWC T3 to 10G adaptor. I have no idea about your PC. If I am wrong, and you are using a Mac (you just said about the macOS SMB client) -
make sure to have SMB signing disabled in terminal, and reboot your machine. And enable Jumbo Frames in both System Preferences for your 10G port, and on the QNAP 10G port.
Why are you only using 6 drives in a TVS-873 - put eight drives in there. If you follow my instructions, you will get 800 MB/sec (and probably not more than 500 MB/sec write).
And stop staring at the specs on the QNAP website (2300 MB/sec) - I have no idea of what they are referring to. With a 10G connection, even theoretical bandwidth can never exceed 1250 MB/sec, and in real life, I have never
seen over 1100 MB/sec on ANY 10G client - no matter what. 2300 MB/sec probably means total aggregate bandwidth - and there is no way that a TVS-873 is going to perform like this. There is real world, and there is fantasy.

Bob Zelin

I have a MacBook Pro with macOS on it. I am going to get my windows boot drive to work again today, and try it with that.
I am of course not expecting the QNAP website specs - they used a RAID5 with 8 ssds and a dual 10GbE link (link aggregation) [And with that, their speeds are actually possible]. But since, the RAID controller seems to be able to do that, and since internal speed tests reports speeds of around 10GB/s on my setup currently, I was simply expecting to get ~900MB/s read on my client machine, especially since the 10G connection appears to work correctly (9.88Gbits/s). Jumbo frames are enabled and SMB signing is off.
I actually am kinda fine with 550 and 400, but today noticed speeds dropping significantly when the qnap cpu is under any load. Did I simply buy an underpowered NAS? (When running a Virtual Machine on another Volume (M.2 SATA SSD) speeds drop to 220 read and 200 write, which is quite disappointing). I think I was just misled by the specs on the qnap website, thinking this NAS is ok for me since they showed it able to do way over 10Gbit/s.
If what I want is impossible with this NAS, could you recommend me a NAS model that CAN actually reach 10Gbit/s with a 6-drive RAID5? And also, I see no reason to use a RAID6 for stuff that is backed up somewhere else anyway. RAID6 is still not a backup.

I see no reason to use a RAID6 for stuff that is backed up somewhere else anyway. RAID6 is still not a backup.

Correct, RAID6 is not a backup. Never said that it was. The point is that RAID6 will help shield you from total loss of the NAS configuration. If two drives were to fail under RAID5, you've lost everything and will have to rebuild the RAID from scratch and then restore everything. On the other hand, with RAID6 you have to lose three drives before this happens.

If, during a rebuild with RAID5, you lose another drive while the rebuild is occurring, you are toast. But, with RAID6, you can lose another drive and get the rebuild to complete.

While this isn't perfect, you stand a better chance of not having to spend lots of time rebuilding your NAS and restoring data.

I now wanted to try this with Windows, but on windows I can't seem to get the 10GbE card to perform the way it should be.
I already tried setting the Jumbo packet size to 9000, is there anything else I need to do?
iperf is only reporting 2.31Gbit/s.

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Mr Robske writes -
If what I want is impossible with this NAS, could you recommend me a NAS model that CAN actually reach 10Gbit/s with a 6-drive RAID5?

This is what drives me crazy about QNAP. They have TOO MANY MODELS, and it's too confusing to figure out the specs on what will - and what will not - perform.
I repeat this exact line over and over on this forum. People ask me all the time "how do you know all this stuff". I DO NOT know all this stuff. I just install a lot of QNAP
products, and some work great, and some work terribly. The TS-873 is ok, but it's not great. Would any model 6 bay that I recommend work to your spec ? I don't know.
I can tell you that if you have the TVS-872XT, that is a GREAT QNAP. You put eight 7200 RPM drives in there, and you will get your 1000 MB/sec on your PC, and about 800 - 900 MB/secREAD on your Mac (write will be slower on the Mac - I don't know why).

SO - will the TVS-672XT do the same job for you ? I don't know. Never tried it. I have tried plenty of 4 and 6 bay QNAP's (like the TS-453BT3) - and it's slow - like 450 MB/sec slow.

Mr Robske writes -
If what I want is impossible with this NAS, could you recommend me a NAS model that CAN actually reach 10Gbit/s with a 6-drive RAID5?

This is what drives me crazy about QNAP. They have TOO MANY MODELS, and it's too confusing to figure out the specs on what will - and what will not - perform.
I repeat this exact line over and over on this forum. People ask me all the time "how do you know all this stuff". I DO NOT know all this stuff. I just install a lot of QNAP
products, and some work great, and some work terribly. The TS-873 is ok, but it's not great. Would any model 6 bay that I recommend work to your spec ? I don't know.
I can tell you that if you have the TVS-872XT, that is a GREAT QNAP. You put eight 7200 RPM drives in there, and you will get your 1000 MB/sec on your PC, and about 800 - 900 MB/secREAD on your Mac (write will be slower on the Mac - I don't know why).

SO - will the TVS-672XT do the same job for you ? I don't know. Never tried it. I have tried plenty of 4 and 6 bay QNAP's (like the TS-453BT3) - and it's slow - like 450 MB/sec slow.

Bob Zelin

Than you for your insights!
The TVS-872XT is already so expensive that I am cheaper off with buying an mac mini (even with built-in 10GbE port) and a thunderbay6... So that won't work for me.

I was now able to get read speeds of around 1000MB/s on windows, and write speeds around 450MB/s. Still disappointed at the write speeds, but I am happy that I can read really well now.

since you are getting good speeds on your TS-873, let me tell you my experience, which is similar to what Trexx is seeing.
I install a lot of TVS-872XT systems. With a Mac, using the QNAP QNA-T3-10G1T, I get between 800 - 900 MB/sec READ and about 500 - 550 MB/sec WRITE.
If I put a QNAP QXG-10G1T into a x4 lane slot in a good Win 10 PC, I get 1000 - 1100 MB/sec READ and about 550 MB/sec WRITE.

If I take these same computers, and put them on a QNAP TS-1677X or TS-1685 (into the native 10G port, with the same 10G switch) - my WRITE speed goes up to about 800 - 900 MB/sec.
Why ? I have no idea, and I have no interest in torturing QNAP on the theoretical limits. Do you know why ?
Because I can take a 2012 Mac Pro, running macOS 10.13.6 with a QNAP QXG-10G1T, and plug it into a TS-1685, and I will get 900 MB/sec READ AND WRITE. I plug a brand new iMac Pro into the same TS-1685
using the native 10G chip in the very expensive iMac Pro (which uses the Aquantia AQC-107 - same chip as QNAP uses for many of these products, and all their new 10G adaptors) - and I get 900 - 1000 MB/sec READ, but
only about 300 - 350 MB/sec write. I have seen this over and over again. Which is why I always try to convince my customers with iMac Pro's to STILL purchase a QNAP QNA-T310G1T or Sonnet Solo 10G T3, instead of
the native port.
WHY ? I have no idea. And I certainly can't call up Apple and start to complain to them - because they will say "bring it to the genius bar" - and the "genius bar" will find nothing wrong (because they are just
plugging the 10G port of the iMac Pro into the internet, and the kid says "looks like it works fine to me".
This is what REAL LIFE testing is about. Some products work better than others. I think they call this "clinical trials" in the medical field. Some drug comes out with a drug that cures, XYZ, they convince doctors
that it's safe - the doctor gives it to you and all his patients, and then YOU get sick, but the others are cured. WHY ? I don't know - and neither does the doctor (and neither does the pharmaceutical company, until
they get sued, and start to research it).

AND if you are a Mac user - well, just wait until macOS 10.15 Catalina comes out later this year - then everything will stop working.

I have an old Asus i7/16GB/SSD-drive/1Gb lan desktop computer with Windows 10 and I can get maximum read ~980Mbits/s and write ~950Mbits/s when copying big Blueray files. When copying photo files I can get maximum read ~600Mbit/s and write ~500Mbit/s.

I have already ordered 10Gb-cards to my PC and QNAP and planning to buy three more HDDs. Let's see how this madness is going to end.